Telephone-exchange system



Feb.;14, 192s.

' E. H. CLARK TELEPHONE EXCHANGE SYSTEM 9 Sheets-Shes n SVKMR m Km fit Rm wt 6% w mRm, Y

Feb. 14, 1928. 1,659,083

E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27, 1925 9 Sheets-Sheet 2 E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27, 1925 9 Sheets-Sheet 5 Q U fdyar 04M Feb. 14, 1928. 1,659,083

E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27. 1925 9 Sheets-Sheet 4 hvenfm .[dyar/z f/ark Feb. 14, 1928.

E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27, 1925 [dyar 674M I 4 Feb. 14, 1928. I 1,659,083

. E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27, 1925 9 Sheets-Sheet 7 JEEP Feb. 14, 1928.

E. H. CLARK TELEPHONE EXCHANGE SYSTEM Filed June 27, 1925 9 Sheets-Sheet 8 Patented Feb. 14,1928.

UNITED STATES mean it. CLARK, or RICHMOND HILL, nnwYon As'sreu'on T0 wnsrrnnu nnnc- TRIO COMPANY, INCORPQBVAEEED, YORK.

TELEFHONE-EXGHANGE s srnm.

This invention relates to telephone ex change systems and more particularly to telephone systems wherein automatic switches are en'iployed for the establishing and'controlling of connections. I

Heretofore in telephone systems employing switches offche coordinatetype such as the syst'em'disclosed in U. S. patent to S. B. l/Villiams, J 1:, No. 1,517,331, issued December 2, 1924, it'has been the practice totarrange subscribers lines as calling lines in groups, each group of lines appearing before a single line switch, Associated with each line switch for controlling the operation thereof is a master control circuit. When for any reason the master circuit becomes inoperative it has been the usual practice to replace such circuit by an emergency or substitute circuit.

' line Under such concitions it necessarily follows that the emergency apparatus is ei'nployed at con'iparatively infrequent intervals. Fur thermore in such systems each calling line. for the purpose of extension, has access to the horizontalv links of choline switch alone *and to only those trunks appearing in this switch. Accordingly when a calling line en'- counters either an all links or an all trunks busy condition in the switch before which it appears the extension of such line may be temporarilyretarded until an idle link or an idle trunk occurs. i

It is an object of this inventiontherefore 'to provide a highly eflicient arrangement of switches and controlling circuits therefor.

Accordingto one feature of the invention each subscribers line has an appearance before a plurality of coordinate line switchesQ to the means forextending calling line of a regular and an emergency master switch 1 1 Another feature of the invention relates to or new YORK, N. Y., Loom-cannon or NEwthe means whereby repeated attempts are made to extend a calling line whentrouble' exists in both the first choice switchnnd in the second choice switch. 1 i

Other features and advantages of the invention not specifically enumerated, above will become apparent after a consideration of the followingv descriptions and the ap pended claims."

Referring to the": drawing, Fig. "1 shows a portion of a master control circuit associated with a. particular line switch. This figure also represents schematically a: trouble indicator, and means for connecting thetrouble indicator to the control circuit:

Fig. Qshows the remaining: portion master circuit partially shown in Fig. 1.

Fig. 3 shows a pluralityof groups of call.-

ing lines together with certain allotting and controlling'relays.

Fig. 4 illustrates a portion of a coordinate lineswitch.

Figs. 5 and 6 show second mastercontrol' circuit associated with a corresponding line switch. p

Fig.7 shows groups of subscribers lines and associated allotting and control relays. Fig. 8 shows 7 a second coordinate line switchsmf' o p I K Fig. 9 isa schematic representation of one form of carrying out the invention.

Fig. 10 represents the manner in which the various sheets of the-drawing are to be arranged for the purpose of obtaining a unitary disclosure of the. invention.

Generaldescription of circuits and apparams. j'

The line switches 400 andSOO are of the coordinate type such as shown and described in U. S.;patent to J. N. Reynolds 1,507,140; SeptemberQ. 1 924, and further shown and described in U. S. PalIEHlZ'tO'S.-B.'W1lllEtII1S, J12, 1,517,331, December 2, 1924. -.Each switch comprises groups of vertical rows of contacts, one group beingallotted to lines and another group allotted to trunks. Each vertical row of contacts has anoperating is the magnet individual thereto for preparing the associated row. For the purpose ofinterconnecting the lines and trunks there are necting magnet as described in provided groups of horizontal link circuits,

each link circuit having a corresponding operating magnet. WVhen a line vertical magnet, a trunk vertical magnet and a horizontal connecting magnet are operated in sequence a connection is established through the switch. The operated line and trunk magnets may thereupon be released and the established connection maintained by the continued energization of the horizontal conthe above mentioned U. S. patents.

It will be noted that the link circuits in switches 400 and 800 are divided into groups, and calling subscribers lines may also be considered as arranged in groups corresponding to the groups of link circuits. For example, lines 301 and 807, etc. appearing before group 811 constitute the A group of subscribers lines. Similarly the group including line 302 constitutes horizontal group B, and so on for succeeding horizontal groups. Each master circuit may be considered divided into horizontal and vertical group controls. For example. the portion of the master circuit appearing in the upper portion of Fig. 2 is effective when any line in group'A initiates a call. The portion of the control circuit shown in the central portion of Fig. 2 controls the extending of lines in horizontalv group B. A similar arrangement exists in connection with the groups of links in switch 800 and the horizontal control groups of Fig. 6. The calling subscribers lines may furthermore be considered as divided into vertical groups, each vertical group comprising all the lines appearing in a particular row of vertical contacts- Each vertical row of contacts has associated therewith a relay. as relay 403, controlling the operation of thecorresponding vertical magnet. The portion of the master circuit shown in Fig. 1 is common to all the horizontal control'circuits of Fig. 2 and all the vertical. control circuits. Similarlv the portion of the master'switch shown in Fig. 5 is common to the horizontal group control circuits of Fig. 6 also to the vertical control circuits.

Each subscribers line has an appearance before corresponding rows of contacts in both switch 400 and in switch 800. For ex- 301. 302. 307, etc, shown in Fig. 3 have switch 400 as their first choice line switch as their first choice whereas the master circuit of Figs. 5 and 6 is normally associated with switch 800 and serves as the first choice master circuit in controlling the extension of lines having as their first choice switch 800. Should any of the lines shown in Fig. 3, upon initiating a call, encounter an all links busy or an all trunks busy condition in switch 400 the master circuit of Figs. 1 and 2 is replaced by the master circuit of Fi 5 and 6 and the calling line is extended through switch 800 under the control of the master circuits of Figs. 5 and 6. Similarly should an all trunks busy or all links busy condition exist in switch 800 when lines 701, 702, etc, initiate calls, then the master 2 General description of met/50d of operation.

Referring to 9 a general description will now be given ofthe arrangements shown in detail in Figs. 1 to 8. lt will be'notcd that the designations employed in Fig. 9 are the same as those employed for corresponding apparatus illustrated in the detailed drawing. In Fig. 9 two coordinate line switches 400 and 800 are shown. as well as two subscribers lines 307 and 701. Each line is multipled to appearbefore switch 400 and switch 800. Switch 400 servos a first choice switch for the extension of line 530?. while switch 800 is a second switch for line 307. On the other hand switch 800 is the first choice. switch for line 701 while switch 400 is the second choice switch for line 701. But one group of links in each switch is shown. in practice, however. each switch comprises a plurality of groups of horizontal link circuits.

Should. a call be initiated on line 307. line relay 303 operates and in turn operate start relay 203 by means of a circuit through left back contacts of relay 201. Relays 201 and 203 are each common to the group of links 411 in switch 400. Should the master control circuit which is individual to switch 400be idle when relay 203: operates, relay 101 is normal, and battery is extended through the contacts ot'relay 101, back Contact? of relay 501, right Winding of horizontal group relay 206, contact-sot relay 203, to grouno at the contacts of relay Relay 200 immediately locks in series with relay 101 and renders the master circuit busy. The cut-in relay 105 is now operated and closes a circuit for the particular vertical group relay which is individual to the row of contacts of switch 400 wherein line 807 appears. In this c relay, 405 is operated by ineanso't acircuit including battery at the contacts relay 107, right winding of relay 05, inner contacts of relay 105, to ground at, the contacts of line relay 30S. Relay 405 immediately locks in series with relay 107. Shortly thereafter relay 108 operates and carr es the operation of vertical magnet 118. At this time magnet corresponding to an idle trunk, such as 451, is also operated. A horizontal magnet such asellil corrcspondinglio an idle link in group 4-11 is thereupon operated, and line 30'? is extended to trunk by means of this idle link circuit. Vertical magnet-s 4'08 and 418 as w-ellas the master control circuit may be released for usein extendingother lines. 0

Should the call be initiated .on line 701,

this line would normally be extended by' means of switch 800 under control ot' the master circuit which is individual thereto.

t will be een therefore that it calls are initiated on lines 307 and 701 simultaneously that each of these lines may be extended throughits first choice switch without awaiting the extension of the other line.

The portion of the control circuit within the dotted rectangle represents switch-over apparatus for allowing a callingline to be.

the line switch. Should all the ks in I group 411 be busy'when. the call 18 initiated,

the link allotting'. relays 305. 306. etc. are all operated and a series circuit exists through the front contacts of these relays tor operating links-busy relay 30S. Relay 308 in turn operates relay 201 by means the'le'tthand winding of thislatterrelay. Relay 201 also operates relay 208. Relays 201 and 208 open the energizing circuit of start relay 203 and closes the energizing circuit of the start relay 603. Relay 603 isindividual to the group of link circuits in switch 800 tacts of relay 201.

before which calling line *307a1s0 appears. The circuit for operating relay 603includes back contacts of relay 619'and front contacts o j'relays' 20b and 303. Line 307 may now be exteiuledthrough switch 800 as a result or: operation or start relay 003."Single call relay 50L is operated at this time by 0 means of a circuit ii eluding right front connot 81? energized. iissuming trunk 853 to be idle trunk vertical magnet 809 is energized. Ashort interval later horizontal magnet 81 operates and line 30; is extended to trunk 853.

Horizontal group relay it instead of an all links-busy condition,

the callingline encounters an all trunkshusy cone. ion, a series circuit is traceable through the front contacts of the trunk a1- lottingielaysflOl, 402 etc.,-to operate relay 119. lielay 119 in turn causesthe operation otrelay' 201b 'i'neans of the right winding ot thislattm' relay. Relay 201. releases relay 203 and. operates relay 003 2153 already (le scribed and the calling line 307 may be extended to an idle trunk appearing before SWlLCllSOO.

The circuits are also arranged in such a through its first choice switch within a period oi. tine counted by a time measuring device, the cur uit will be closed for all the relays similar to relay. 201 associated with the first choice switch. .iiccordingly when any lines which have this switcl1,..tor their first choice have call initiatedthereonythese same lines will be extended through the second choice switch as will appearftroin the detailed descr ption given hereinafter.

Detailed description of aqconnccrfe'oa insole-' 7112;; a firsthlioice sic-itch alone.

It will be line 301 has initiatedia call by the removal of the receiver from its switch-hook, and that at thetiine the call is initiated, trunk alone, is idle. As noted hereinbefore A links all inswitch 400 serve as a first choice group tor the extension of line 301, while group otlinks 811 in switch800 -iristitute a second choice. group. For the present it will be assuz'nedthat link in the first choice switch e00 is idle. hen the subscribers loop circuit is closed by the removal oi the receiver, line relay 303 'inanne'r that it a calling line'is not extended assumed that the subscriber of y operates by means of a circuit including the closed calling line and the back contacts of cut-off relay 304. A circuit is thereupon completed for start relay 203 which is common to the subscribers lines appearing before group of links 411. In a similar man ner relays 204 and 205 are each common to their respective horizontal groups of lines. F or the present it will be assumed that line 301 is the only line upon which, at this time, a call is being initiated. Accordingly, relay 203 completes a circuit for horizontal group relay 206, this circuit being traced from ground at the left back contacts of relay 502, back contacts of relay 503, conductor 553, conductor 651, inner front contacts of relay 203, right winding ofrelay 206, right outer contacts of rela Y 207, conductor 253, back contacts of relay 501, conductor 101, left contacts of relays 101 and 112, to battery at the contacts of relay 114. A circuitis also completed at this time for relay 102. This circuit may be traced from battery through the winding of relay 102, conductor 254, left outer contacts of relay 207, to ground at the left contacts of relay 203. The function of relay 102 will be described in detail hereinafter. With relay 206 operated a locking circuit is completed for said relay, this circuit including the left winding and locking contacts of relay 206, winding of re L lay 101. and battery at the left contacts of relay 108. Relay 101 operates over this circuit. Relay 206 also completes an obvious operating circuit for relay 202. vRelay 202 by means of its make-before-break contacts closes substitute holding circuit for relay 303. This circuit may be traced from battery at the left outer contact of relay 104, left front contacts of relay 202, conductor 251, back contacts of relays 201, 208 in parallel, conductor 351, winding of relay 303, to ground as hereinbefore traced. Relay. 101 in operating as above described, closes an obvious energizing circuit through the right winding of vertical group start relay 104. Relay 101 also extends ground through its right inner contacts over conductor 155 to provide a temporary locking circuit for tl e trunk relays 401 and 402, etc. This locking circuit is provided to prevent a previously operated trunk relay from releasing during the select on of an idle trunk as will appear from the following descriptions.

Circuits are now prepared for the vertical group relays 403, 404, etc., by means of the mult-i-contact relay 105. The circuit for operating relay 105 may be traced from battery through the Winding of said relay, conductor 156, right middle contacts of relay 206, conductor 255, rightouter contacts of relay 106, to ground at the right contacts of relay 104. Since line relay 303, alone, is operated, a circuitis completed for vertical group relay 403 which is individual to vertical row of contacts 406 wherein the call ing line appears. The circuit for operating relay 403 may be traced from battery at the right back contacts of relay 107,.conductor 157, right winding of relay 403, conductor 356, left outer contacts of relay 105, conductor 352, to ground at the contacts of relay 303. Relay 403 locks by means of a'circuit which includes the grounded conductor 356, left winding and locking contacts of relay 403, left back contacts of relays 404 and 105, conductor 455 and battery through the wind ing of relay 10?. Relay 10'? operates in this circuit to prevent the operation of any other of the vertical group relays 404, 405, at this time. Relay 107 now causes the operation of relays 103 and 109 by means of a circuit including the operating windings of these relays in parallel and left front contacts of relays 107 and 102. Line vertical magnet '10 is now energized over a circuit traceable from ground through the winding of said magnet, right outer front contacts of relay 403, conductor 456, to battery at the contacts ofrelay 108. Since the trunk 453 is busy, relay 401 individual thereto is operated and a circuit is completed at this time for trunk vertical magnet 408. This circuit may be traced from ground through the winding of magnet 408, right back contacts of relay 402, right front contacts of relays 101 and 403, conductor 154, to battery at the contacts of relay 108. Line vertical control relay 111 is now energized over a circuit traceable from, battery through both windings of said relay in series, conductor 151, to ground at the contacts of magnet 407. Relay 111 in turn closes an obvious operating circuit for relay 112. Trunk vertical control relay 113 is also operated at this time over a circuit traceable from ground through the left winding of said relay, right back contacts of relay 114, (2011- ductor 152, lower front contacts of magnet 408, conductor 457, to battery through the middle winding of sender selector'start relay 801. Both relays 801 and 113 operate in this circuit. Relay 801 locks under control of relay 803. The operation of relay 801 serves to bring about operation of a sender selector switch shown schematically by the rectangle 802. For a detailed description of the man ner in which the relay 801 may function to cause the operation of a coordinate sender selector switch, reference may be had to the U. S. patent to S. B. WVilliams, J11, No. 1,517,331, issued December 2, 1924.

After an interval relay 113 closes its front contacts and extends ground from the lower middle contacts of magnet 408, through the said frontcontacts of relay 113 through the winding of relay 114 which begins to attract its armature. After an interval, the contacts of relay 114 close and a circuit is completed from battery through the right S. B. Williams, Jr., hereinbefore referred to. Relay 803 operates and opens the hold 111g circuit of start relay 801 which releases.

Relay 115 being marginal does not operate in series with the resistance of the right.

hand winding of relay 207. When relay 207 closes its innermost front contacts, the resistance of the right winding is short circuited and a C11Ctllt 111Zly now be tracedtrom battery through the middle win ding of relay 207, innermost right contacts of said relay, and thence to ground through the winding of relay 115 as'above described. A circuit may now be traced from battery through the lelthand low resistance winding of magnet 413, right outer back contacts of relay 305, right outer front contacts of relay 306, conductor 363, innermost right front contacts of relays 207 and 206, and thence through the winding of relay 115, over conductors 152, and 457 to ground at the contacts of relay 803. Relay 115 receives sutlicient current by means of this circuit to enable said relay to operate. This last traced circuit for operating magnet e13 acts as a shunt around the right winding of relay 305. When magnet {L13 has completely operated, a circu t is completed from battery through both windings of said magnet in series, thence through contacts ot'switch l00 to the sleeve conductor of trunk 45.1,which may be grounded at a succeeding selective stage in a manner similar to that described in the above mentioned patent to S. B. Williams, Jr; This same ground is extended by means of switchl00 to the sleeve conductor of line 301 causing relay 304 to operate. Itelay 304 in turn. brings about the, release of relay 303. Q If there are no other calling lines await ing extension, then the release of relay 303 brings about the release of relay 203. Relay 303 also removes ground from con ductor 352, whereby the holding circuit of relays 103 and 107- is broken and these relays release. Relay 4103 in releasing causes the deenergization of line vertical mag;

. net 107. Belay 203 opens the holding circuit otrelays 200 and 101, both of these relays now being deenersgized, 107 and 104; normal, both relays 108 and 109 release. Release ozt relay 108 removes the operating battery for trunk vertical magnet I 41-08 which in turn deenergizes. As soon as magnet 108 closes its lowermost back con tacts, the grounded conductor 457 is ex lVith relays tended through the right winding of relay l02 which operates to render trunk ltil busy.

The multi-contact relay; 105 was released when group relay206 opened its right mid: dle contacts. Relay 206 upon opening its inner righteontacts removes ground from conductor 353. Conductor 353 being thus disconnected from ground. the sh-unt is re-. moved from around the right winding of relay 305 which now operates over an ob vious circuit to ground at the left contacts of magnet 113. Magnet 413 remains operated through both windings in series as hereinbetore described. The masterv circuit associated with switch 400 is thus completely restored, and line 301. is extended through link Q12 to trunk 1:51.

Should calls be initiated on two or more lines thesame horizontal group but in diiferent vertical groups, one

simultaneously line will be given the preference as regards extension by switch 400. For example, should lines 301 and 307 call simultaneously, then line 307 would extended, first. As described hereinbe'tore the operations will proceedias far as the .point where the ver tical group relays 403, 404, etc., have their locking circuits prepared. It will be noted, however, that relay 404- being nearer to the grounded conductor 455 will remain locked in series with relay 107, thus causing the release of relay 403. Should all links in second choice group 811 be busy at this time relay 403 remains normal until line. 307 is extended through switch 400,- whereupon the 'naster circuit shown onFigs. 1 and 2 may be taken into useagain forthe extension of line 301. p i

Should calls be initiated ontwo or more lines, in diilerent horizontal groups but in '101asalready described. Belay 206, there tore, remains locked and brings about the release of relay 21a. Thus line 307 may be extended first, after which, line309 may be extended. Should however the master circuit of switch 800 be available, line 309 need not wait but may be extended tthrough its second choice switch as will be described hereinafter.

hen a calling line must await its turn as above described, the line and start relays- 303 and 203 are retainedoperatedready to cause the energization of the corresponding mal; of relays 111, 112 and 107 108.

horizontal group relaysuch as 206 as soon-l "Provision is also made-for giving equal service to the differentfhorizontal groups of i mentioned.

lines regardless of the a preference above For example, should calls be initiated simultaneously on line 302 in horizontal group B and on lines 301 and 307 in group A, then as above noted, the preference will be given to that one of the lines in group A whose vertical group relay is nearest to the holding conductor 4:55, consequently line 307 will be extended first. During the process of extending line 307, relays 101 and 206 are operated as already described. Since a call is now awaiting in group B, relay 20a is operated, consequently relay '102 remains energized until the line in group B is extended. So long as relay 102 is ope ated a locking circuit is provided for relay 207 through the left winding thereof. Therefore, relay 207 remains locked until line 302 in group B has been extended. As long as relay 207 remains locked, the ope-rating circuit of horizontal group relay 206 is opened and line 301 in group A cannot be extended until the waiting line 302 in group B is extended, whereupon relay 210 remains locked under control of relay 204. With relays 207 and 209 simultaneously locked, relay 102 releases, in turn bringing about the release of relays 207 and 209. Line 301 in group A may now be extended.

Description of a connection involving a second choice switch.

to ground through the winding of relay 308.

Both relays 207 and 308 operate in this circuit. The operation of relay 207 serves as an indication to the master circuit that all links in group 111 are busy. Relay 303 atv its left inner contacts closes an obvious operating path through the left winding of switch-over relay 201. Relay 201 at its left outer back'contacts opens the circuit of relay 203 which thereupon releases. It will be assumed that the master circuit associated with switch 800 is idle at this time. A circuit may, therefore, be traced from battery through the winding of slow releasing relay 503, innermost back contacts of relay 501, conductor 555, conductor 653, right outer contacts of relay 201, conductor 257, left'inner contacts of relay 117, conductor 556 to ground at the contacts of relay 516. Relay 503 completes a circuit from ground at the left contacts of relay 502, front contacts of relay 503, left inner contacts of relay 505, conductor 158, left inner contacts of relay 104;, conductor 159, to battery through the winding of Inulti-contact relay 501. Relay 501 im mediately closes a locking circuit for itself 'raceable from battery through the winding and locking contacts of said relay, conductor to ground over conductor 653 as above traced. Relay 208 now operates by means of a circuit which is completed from battery through the winding-of said relay, left inner contacts of relay 201, conductor 259, conductor 654-, to ground at contacts of relay 501. Relay 208 in turn causes the energization of start relay 603 which is common to thos lines appearing before group 811 in switch 800. The circuit for operating relay 603 may be traced from battery through the winding of said relay, left outer back contactsof relay 608, conductor 260, right front contacts of relay 208, conductor 261 to ground at the contacts of relay 303. It will be noted that the operating circuit for relay 303 now extends from battery at the left contacts of relay 10d, conductor 551, next to innermost front contacts of relay 501, left outer back contacts of relay 505, normal contacts of relay 60%, left inner back contacts of relay 619, left inner front contacts of relay 208, winding of relay 303, to ground at the contacts of relay 304. .Vhen relay 501 operated, the energizing circuit of relay 503 was broken and this relay began to release. fter the interval measured by the release of relay 503, a circuit is closed for horizontal group relay 601. This circuit may be traced from ground at the left back contacts of relay 502, back contacts of relay 503, conductor right inner contacts of relay 603, right winding of relay 601, right back contacts of relay 607, conductor 655, left con tacts of relay 504, left back contacts of relays 504, 512 and 514, front contacts of relay 501, conductor 553, left contacts of relays 101 and 112, to battery at the left con tacts of relay 11 1-. When relay 601 closes its contacts, the grounded conductor 651 is extended through the left winding and locking contacts of relay 601, thence through the winding of relay 504C to battery at t e left contacts of relay 510. Relays 601 and 504 operate in this circuit and render the master circuit of switch 800 busy. Relay 601 closes and obvious energizing circuit for relay 60s and relay 50d completes an obvious circuit for relay The circuits are now in condition to cause the operation of a line vertical magnet and a trunk vertical magnet associated with switch 800. For this purpose relay 507 is energized over circuit traceable from battery through the winding of said relay, left middle contacts of relay 601, conductor 656, right outer contacts of relay 517, conductor 564C, to ground at the contacts of relay 505. Since line relay 303 is operated a circuit is closed for vertical group relay 803 which is individual to the vertical row of contacts 806 wherein line 301 appears. The circuit contacts of relay 508, conductor 558, right winding of relay 803, conductor/751, left outer contacts of relay 507, conductor 559, innermost contacts of relay 506, conductor 162, conductor 352, to ground at the contacts of relay 303. Relay 803 locksthrough its left winding and locking contact in series with the winding of relay 508. Relays 509 closed from battery through the right wind' and 510 now operate in a manner similar-to that described for relays 108 and 109. Line vertical magnet 807 is now energized by means of a circuit traceable from ground through the winding of said magnet, right outer contacts of relay 803-, conductor 752, to battery at the contacts ofrelay 510. Assuming trunk 853 to be idle then the associated trunk relay 810 is normal, and trunk Vertical magnet 809 operates over circuit from ground through the winding of said magnet, right back contacts of relay 810,

right inner contacts of relay 803, conductor 753, to battery at the contacts of relay 510. It willbe noted that vertical magnet 807 causes the successive operation of vertical control relays 511 and 512 over circuits similar to those described for relays 111 and 112. Similarly the trunk vertical magnet 809 completes circuits for operating relays 513 and 514, these circuits being similar to those described for relays 113 and 114. WVith relays 511 and 514 operated, a circuit is ing of relay 607, thence through the right innercontacts of relay 601, conductor 657, right outer contacts of relay 511, winding of relay 515, right front contacts of relay 514, conductor 658, lowermostfront contacts of magnet 809to conductor 854. Conductor 854 may be connected to battery through the middle winding of a sender selector start relay similar to relay 801 for the purpose of associating an idleisender with the trunk 853, as described in connection with trunk 451. The operationi of a horizontal magnet such as 813 corresponding to the first idle link in group 811 is similar to that described in connection with magnet 413 and it is believed that further description of this method of operation is unnecessary. Assuming that magnet 813'has been thus operated, the grounded sleeve conductor of trunk 853 is extended through contacts of switch 800, thence over the sleeve conductor of line 301 to operate relay 304. Relay 304 causes the successive release of relays 303 and 603. l Vith relay 603 restored to normal, the release of the master circuit shown in Figs. 5 and 6 is similar to that described in connection with the master circuit of Figs;

1 and 2 and further description is not deemed necessary. Itwi1l be noted, how-,- I

ever, that switch-over relay 201-and multicontact relay 501 remain operated so long as a all links in group 411 are busy. 1

I In thepreceding:description it has been assumed that the master circuit associated with switch 800 was idle'whenthe call was initiated on line 301. Should the master circuit have been busyat the time, then rea lay- 504wwould be operated and line 301 would awaittherelease of the second choice master :Cll'C'LllliLl While thus waiting itmay happen that one of the links in group 411 becomes idle, whereupon relays 308, 208, 201,

and i501 release. The calling line 301 under thiscondition may be extended over theidle link in group 411under control of the mass ter circuitassociatedwith switch. 400 as described. hereinbefora Should the call beginitiated on a line, for

example line 701, whose first choice switch is switch 800, and assumingthere to be an idle link tin-fr the corresponding group of links, thenli ne 701 will be extended under control of themaster circuit which is individual to switch 800 and shown in Figs. 5 and '6. The

sequence of'operations in such a case is sub-,

stantially, similar to that described in con nection with the extension 0f line' 301 through link 411 under control of the master circuit of'Figs. 1 and 2.

Should all the links in group 811 be busy when the call is initiated on line 7 01, then relays 708,y608, 619 and501 are operated similarly to the manner in which relays 308, 201, 208 and 501 were operated when an all linksbusy condition-existed in group411. Should there be anidlelink in group 411 when line relay 703 operates, relays 201 and 208 associated with group 411 are normal. Accordingly when relay 703 operatesa circuit may be traced from ground through the .1 front contacts of relay 703,-thence over conductor 660, right front contacts of relay 619,

conductor 659,-;lettouter back contacts of re-' loo lay 201, to Zbatteryt-hrougl'r the winding ofstart relay 203. \Vhen relay 203 operatesa circuit isv closed for group r elay 206, trace-4 able from ground atthe back contacts of relays 502 and 503, conductor 553, conductor 651, inner front contacts of relay" 203, rightwinding of relay 206, right-back contacts of relay 207, conductor 253,,front contacts of reright winding of relay 404, left front con-- tacts of relay 105, conduct-or 176, left I front contact of relay 506, conductor 573, to ground at the front contacts of relay 703. Relay 404 looks in series with relay 107 whereupon relays 108 and 109 operate as already described. Line vertical magnet 407 and a trunk vertical magnet corresponding to an idle trunk appearing in switch 400'are now operated. The further selection of an idle link in group 411 and the operation of the corresponding horizontal magnet is controlled in the same manner as that described in connection with the extension of line 301 through switch 400.

All trunks busy.

I Should all the trunks appearing in the first choice'switch be busy when a line initiates a. call, all the trunk relays associated with said switch are operated. F or example, should all the trunks appearing in switch 800 be busy when line 701 initiates the call, then relays 810, 814, etc.,' are operated. A circuit is thereupon completed for relay 522 traceable from battery through the winding of said relay, conductor 561, left outer contacts of relays 810, 814, etc., to ground. Relay 522 extends ground through its outer front contacts over conductor 563, thence in parallel through the right windings of relays 608, 609, 611, etc., to battery. The operation of relay 608 brings about the operation of multi-contact relay 501 as hereinbefore described and the calling line 701 is extended through switch 400 under control of the master circuit of Fig. 1 as already described.

Should all the trunks appearing in switch 400 also be busy when the switch over relays 608 and 619 are operated, then relay 119 is operated over a circuit similar to that described for relay 522. With both relays 119 and 522 operated, a circuit is completed for relay 502 traceable from battery, through the winding of said relay, conductor 552, left contacts of relays 119 and 522, to ground. Relay 502 in operating disconnects the control ground and no callscan be started under control of either of the master circuits until a trunk becomes idle as indicated by the release of relay 502.

Eaufcnsion of a call under trouble conditions.

cause a printed record to be made thereofj For example, as soon after start relay 203 operates, when interrupter .140 closes its lower contacts, a circuit is completed from battery through said contacts, winding of relay 103, conductor 163, outer front contacts of relay 203, conductor 274 to ground at either the back contact of relay 112, or at the front contact of relay 111. Relay 103 completes an obvious locking circuit for itself. After thepredetermined interval interrupter 170 Closes its upper contacts and a circuit is completed from battery, through said contacts, right contacts of relay 103, winding of relay 118 to ground at the right contacts of relay 502. A locking circuit is thereupon completed for relay 118 traceable from battery at the right outer contacts of relay 521, conductor 562, inner right contacts of relay 118, right contacts of relay 103, winding of relay 118, to ground as above traced. W'ith relay 118 operated a circuit is completed from ground at the left outer contacts of relay 117, through the left contacts of relay 118, and thence to the time measuring device 120 whose operation is thereby initiated. The measuring device 120 may be of any well known type and at the end of an interval measured thereby, relay 118 remains operated and conductor 164 is grounded, causing the operation of relays 117, 121 and 106. Relays 121 and 106 immediately look. over a circuit traceable from battery through the windings of these relays in series, locking contact of relay 106, right outer contacts of relay 121, contacts of key 165, right normal contacts of relay 521, to ground at the contacts of key 565. Relays- 106 and 121 thus remain operated independently of the time measuring device 120. The above traced ground. is also extended over conductor 166 to operate the multi-contact relay 167 by means of the noninterferring start circuit 168, as described in the copending application of E. B. Craft and L. Keller, Serial No. 747 ,174, filed Nov. 1, 1924, Patent No. 1,614,285, dated January 11, 1927. The various trouble indicating leads from the master circuit of switch 400 are connectedto a trouble indicator 169. This trouble indicator may be of the general type disclosed in the patent to E. B. Craft and L. Keller referred to above. \Vith relay 121 operated, circuits are completed from battery through the right windings of relays 201, 211, 212, etc, in parallel, and thence] over conductor 272 to ground at the left outer contacts of relay 121. Thus by means of the operation of relays 201, 211, etc., the entire switch 400 and its associated master circuit are removed temporarily from service. With relay 201 thusoperated, the start relay 203 releases, and relay 603 operates. -The calling line 301 may therefore be extended through switch 800 under control of the master circuit of Figs. 5 and 6 as hereinbefore described It will now be assumed that when the line ee-e9 master circuit. A circuit is now completed from battery through the winding of relay 521, conductor 567, right inner contacts of relay 106, conductor 568 to ground-at the left front contacts of relay 518. -Relay 521 immediately locks under control of the key 565. In addition relay 521 opens thelocking circuits or relays 517, 518 and 106, 121.

It will he noted thaturelays 103 and 118 have their loclzing circuits opened when the start relay 203 is released by the operation of relays 201 and 208. When relay 121 releases as above described, it in turn 'causesthe release of' the switch over relays 201, 211 and 212 and the calling line 301 may make ,an-V

other attempt to be. extendec l through," switch 400, .The circuits are so arrangedthat this process' of repeating attempts'to extend the calling line may; be continueduntil the end of the interval determined bythe complete operation of the time measuringidevice 120, whereupon an alarm may be given'to an attendant who mayascertain the gsource and nature of the trouble by means otaprinted record, as describedin the pat ent to Craft and Keller referred to herein- I before. i ,1 i I What is claimed is: A

1.111 a telephone exchange system, telephone lines arr nged in groups, a plurality ot line switches each acting normally as a first choice switch for the lines otone group and as asecond choice switch forthe lines of another group, a plurality ofequivalent trunks appearing in each ofsaid switches, means'responsive' to the initiation of a call on'o'ne of said lines. for causing the operation of a first choiceswitch to the exclusion of a second choice switch to extend said line, and means responsive to the initiation of a call on said line for causing the operation of a second choice switch to the exclusion of afirst choice switch tofextend said line.

2, In a telephone exchange system, a calling line, a first choiceli-ne switch, a second choice line switcheach of said switches comprising links forextending said line, means effective when an idle link exists in s aid first choiceswitch for operating said switch to extend saidline, and automatic1neans re sponsive to an all links busy conditionin said first choice switch :tor operating said,

second choice switch to extend saidlinei 3. In a telephone exchange system, acalling line, a first choice line, switch, a second choiceline switch each of said switches com} prising link circuits for extending said line, a master circuit for each of: said switches, the master circuit of said second choice switch being, normally unable to, C0i O1 the extension of said sline,iandfautomatic means eifective in response to an all links busycon dition in said first choice switch for associating" said second master circuitwith said line said second choice switch. I l

a at. In a telephone exchange system, acallto v cause said line tobe extended through ing line, a plurality of switches in which said line appears each switch comprising a, plurality oi": links for extending saidline, a,

plurality of master circuitseach individual to one of said switches for controlling the' operation thereoh'oneof said master cir i cults being, normally associated with said line, another offsald master circuits being,

normally disassociatedfrom said line, means effective when all the link circuits inone'ot said switches are busy for disassociatingsaid one of'said master circuitsi' from said line and for associating said other of; said" master circuits with said line to causethe sameto be extended through thejsw' tch corresponding to said other master circuit; I

5. In telephone exchangesystem, a callmgline, a first ch'oice l ne switch, a second choice line switch, group of trunks appearing in said first :Choice switch, roup of equivalent-trunksappearing in sai sec? 0nd choice switch',1 a master circuit for each switch, the master circuit-f saidsecond. switch being normally unable -0 control the extension of said lin'e, and means effective. when all the trunks appearing in: said first switch are busy for) associating the master circuit of said secondswitch with said line to cause saidline tobe. extendedby means ofsaid second switch to an idle trunk in said second mentioned group of trunks) 6. In a telephone exchange system, groupsof calling lines, a plurality of line switches I each adaptedto act as a first choice switch .for one group of lines and as a second choice switch for another groupof lines, groups of trunks, each group appearing in one of said switches, means responsive to the initiation of a call on a line for causing one of said switches to act-as a first choice switchto extend said line to an idle trunk'in thcorresponding group, and 'means independent of the line effective whenv allthe trunks in said corresponding group are busy-forcau'sing'another oi saidswitches to act as a second choice switch to the exclusion of a first choice switchto extend said lineto'an; idle trunk.

7.I1iia telephone exchange system, a calling line," a plurality, of line switches in which said line terminates, groups of trunks, each group appearing in a correspond ng line switch, one of, said groups acting as first choice trunks for said line and another of said groups acting as second choice trunks for said line, means responsive to the initiation ota'eall on said lineffor. operating one no i of said switchesto seize an idle trunk in the firstchoice group, and automatic means inde'pendent of the calling line effective when 7 all the trunks in said first choice group are busy for causing another of said "switches to operate to the exclusion of said first switch toselze an ldle trunk 1n saidsecond choice group,

adapted to act as first choice links for said line, a group of links in said second switch adapted to act as second choice links for said line, means responsive to the initiation of a call on said line for causing said first switch to extend] said line by means of anidle link vin the first choice group, and automatic means independent of the calling line etfectlve when all the links in said first choice group are busy for causing said second switch to extend said line: by meansoi a link in said second choice group.

9. In a telephone exchange system, afirst callingline, a second calling line, a first line switch, a second lineswitch, both of said lines appearing in both of said. switches, agroup of trunks appearing in said first switch serving as first choice trunks for said first line and as second choice trunks for said second line, a group of trunks appearing in .said second switch serving as first choice trunks for. said second line and as second choice trunks for said first line, means responsive to the initiation of a call on said first line for operating said first switch to extend said first line to a trunk appearing in said first switch, means effective when all trunks appearing in said first switch are busy for operating said second. switch to extend said first line to a trunk appearing in said second switch, means responsive to the initiation of a call on said second line for operating said second switch to extend said second line to a trunk in said second group, and means .efiective when all the trunks in said second switch are busy for causing said first switch to operate to extend said second line to a trunk in said first switch.

10. In atelephone exchangesystem, a plurality of calling lines, a first choice line switch, a second choice line switch, each of said; lines appearing in both of said switches, a master control circuit for each of said switches, means for operating said first choice switch to extend one of said lines, and means effective when said one of said lines is not extended by said first choice switch within a predetermined time for causing said second choice switch to operate to extend said one of said lines.

11. In a telephone exchange system. a plurality of calling lines, a first choice line switch and a second choice line switch, each of said lines appearing in both of said switches, a master control circuit for each of said switches, means tor-operating said first choice switch to extend one of said lines, and means effective when an unstandard con dition exists either in said first choice switch or the associated master circuit for causing said second choice switch to operate to extend said one of said lines.

12.. In a telephone exchange system, a first calling line, a second calling line, a first lino switch, a second line switch, said lines appearing in both of said switches, a master control circuit for said first switch, a master control circuit for said second? switch, said first master circuit adapted to serve as a normal control in the extension of said first line and as an emergency control in the extension of said second line, said second master circuit serving as a normal control in the extension of said second line and as an emergency control in the extension of said first line.

13. In a telephone exchange system, a call-v effective in response to an unstandard con-.

dition in either said first line switch or the associated master circuit for causing said second mentioned master circuit to be associated with said, line to control the operation of said second line switch to extend said line therethrough.

14. In a telephone exchange system, a calling line, a first choice line switch, a second choice line switch, said line appearing in both of said switches, means for operating the first choice line switch to extend said line, means for operating said second choice switch to extend said line when the same cannot be extended through said first choice line switch, means efiective when said second choice'switch is also unable to extend said line for causing said first choice switch to make a second attempt to extend said line, and means for causing said first and second choice switches to make repeated attempts in succession to extend said line.

15.111 a telephone exchange system, a calling line, a first choice line switch, a second choice line switch, trunks appearing in both of said switches, means responsive to the initiation of a call on said line and effective when all said trunks are busy for causing said first and said second choice switches to make repeated trials in succession to extend said calling line until one of said trunks becomes idle and means for causing the switch in which said idle'trunk appears to operate to extend the calling line thereto.

switches to make repeated attemptsin suc- 10 on said line and effective when all available links in both of said switches are busy for causing said first and said second! choice cession to extend said line until a link in one of said switches'becomes idle, and means for causing the switch in which the idle trunk is located to operate to extend the ca1ling line there-through. V 5

17. In a telephone exchange sy'stem,,a calling line, first choice means for extending said] line comprising a line switch and a master control circuit therefor, second choice means for extending said line comprising a second line switch and a master control circuit therefor, means effective when an 1111'- standard condition exists in said first choice,

means forcausing vsaid line to be extended by said second! choice means, and means effective when an unstandard condition exists inboth of said first and said second choice means for causing repeated attempts to be made to extend said line through said first and said second switches.

In witness whereof, I hereunto subscribe my name this 26 day of June A. D., 1925.

' I EDGAR H. CLARK. 

